Rotary pump and motor hydraulic transmission



Mil EMMA Filed Dec.

, 1953 E w WOYDT ROTARY PUMP AND MOTOR HYDRAULIC TRANSMISSION Dec. 15

Patented Dec. 15, 1953 1 QFFICE ROTARY PUMP ANIP MOTOR HYDRAULIC TRANSMISSION Eduard William Woydt, Stuttgart, Germany Application December 15, 1949, Serial No. 133,070

Claims priority, application Germany December 20, 1948 4 Claims.

The present invention relates to a hydraulic transmission.

More particularly this invention relates to a hydraulic transmission of the type including a pump unit, a motor unit, cylinder blocks for each unit having cylinder bores therein, piston members in the cylinder bores and reaction or eccentric members for reciprocating the pistons.

' Transmissions of this general type are known which embody interconnected pump and cylinder blocks with the means effecting the interconnection also serving as a conduit for flow of liquid under pressure between the pump and the motor. Additionally, eccentric means reciprocate the pistons in the respective blocks and means are provided for controlling the fluid flow to or from the cylinders. The eccentric means include ring members. While such an arrangement reduces friction between the pistons and the eccentrics, a serious disadvantage remains, in that the pump and motor pistons are worn due to their being pressed against the walls of the cylinders.

The present invention has for one object to overcome this disadvantage. Accordingly the reaction or eccentric member of the pump is a rotary non-adjustable ring member rotating with the pump pistons and is connected to the pump cylinder block by a coupling means permitting relative radial movement. Similarly the eccentric means for the motor unit comprises an eccentric ring rotatable on an adjustably fixable eccentric means and connected to the motor cylinder block by a similar coupling means. In this manner, the pump and motor pistons are kept free of lateral forces. This is of particular importance in transmissions having a very short motor stroke for transmitting high turning moments. In transmissions which transmit turning moments by reaction on pistons in cylinder blocks, the pistons, due to their short path of movement in the cylinders wear out very rapidly. This disadvantage is avoided by the use of the coupling means between the eccentric rings and the cylinder blocks and especially if the pressures are transmitted by means decreasing the friction, for example, by rollers.

Furthermore, the prior known transmissions of this type regulate the entry or exit of fluid to or from the working cylinders by rotatable sleeves or slides, located within the hollow means interconnecting the pump and motor cylinder blocks. This arrangement has the disadvantage that the pressure liquid flowing from pump cylinders to motor cylinders is conducted from a 1'0- tating part into a stationary part or a part rotating at another speed. Under these conditions 2 it is difficult and when utilizing high pressures practically impossible to attain adequate packing between the parts so that there is a large loss of pressure liquid, and thus a drop in efiiciency.

This invention has for another object to eliminate such losses in pressure liquid and thus provide the high eihciency. Therefore, to control the fluid flow between the cylinders, control elements are utilized which rotate with the cy1inder blocks. Thus the pressure liquid flows through a hollow rigid interconnection between the pump and motor cylinder blocks to and from the pump and m-ctor cylinders and during its entire flow remains within the rotary body. The control elements are preferably piston type slide valves and to efiect their operations, means, for example, wobble plates are preferably arranged between the pump cylinder block and the motor cylinder block.

Further and more specific objects will be apparent from the accompanying drawing taken in connection with the following description, and in which:

Figure 1 is a longitudinal view, partly in section and partly in elevation, of a hydraulic transmission embodying the invention;

Figure 2 is a transverse view partly in section and partly in elevation and taken on lines II---II of Figure l; and

Figure 3 is a similar view taken on lines III-J11 of Figure l.

In the drawing the hydraulic transmission illustrated includes a fixed and outer casing I having opposite bearings 4 and ll. A central transverse apertured web divides the easing into two halves. Bearing means 25 are arranged in the web. An output shaft 2 is journalled in bearing i and a hollow input shaft 48 is journalled in bearing M. An input gear 13 is embodied with shaft ill and suitable drive means such as an engine or motor not shown impart rotation to gears '53. The shaft 40 is integral with a cylindrical frame or casing 32 which is also journalled by bearing 39 on shaft 42. Frame 32 constitutes a rotor for the pump unit of the transmission. Thus those elements to the right of the central web form the pump of the transmission and those to the left of the web constitute the motor. The frame 32 has an eccentric 38 at one end and an eccentric 3i and a cam 28 at the other. Mounted on the eccentrics through respective bearings 3'1 and 30 is an inner casing or ring it having angle shaped internal guide rings 34 therein. Within the casing 45 is a pump cylinder block 4 3. This cylinder block has radially arranged cylinder bores therein within which reciprocate pump pistons 15a. These pistons have plates Ila on the outer ends thereof and roller means [Ba are interposed between the plates and the inner surface of casing 45. Springs bias pistons [5a toward casing 45.

The motor unit includes an adjustably flxable frame or casing 6 journalled by bearings 5 and 8 on eccentric bosses at opposite end of an inner casing 9. This casing 9 has internal angle shaped guide rings l guiding pistons l carried in radial bores in motor cylinder block I4. Plates H are provided at the outer ends of each piston l5 and rollers l6 are interposed between the plates and the inner surface of casing 9. Springs 41 urge pistons l5 outwardly to press rollers l6 against casing 9. As shown in Figure 2, the-inner periphery of easing 9, between guide rings [0 is provided with four tangentially disposed flat surfaces against which the rollers it contact in order to ensure proper contact and to prevent lateral thrust on the pistons. A similar arrangement is provided within the casing 45 of the pump unit.

The pump cylinder block 44 is rigidly interconnected with the motor cylinder block through a tube 46. This tube 46 is journalled in the bearing in the central web of casing I. The tube 46 is integral with the respective cylinder blocks and communicates at each end with radial bores 48 in the respective pump and motor cylinder blocks or rotors. These bores 48 communicate with further bores disposed parallel with the axis of rotation and in which the control elements constituted by the reciprocable piston or plunger valves lea of the pump and IQ of the motor are movable. The bores receiving the plunger valves communicate in turn through transverse bores 59 with the respective working cylinder bores. To control the valves, wobble plates 20a and 20 are respectively mounted within each casing half. The wobble plate 20a is mounted on bearings 2 la on cam 28 and a flanged tube 53 which is secured to the central web mounts the wobble plate 20 in bearings 2| at its inner end and which end is also a cam. The springs 12 biased between the motor cylinder block and a ring l3 on each plunger 19 urge the plungers to the right in the drawings and keep their rounded ends 29 pressed toward the inside of the wobble plate 20. A similar arrangement urges plunger 911 toward the left in the drawing and against wobble plate 20a. The wobble plates have the shape of an open cone or other concave tapered form so that they always provide a component of force acting radially inwards on the plungers l9 and 9a. The plungers are provided with a reduced portion which permits fluid flow when the plungers are moved to expose bores 50. Since the lungers l9 and Mia. move oppositely it is clear that they control fluid flow through the transmission. When plungers I9 are moved to the left the motor cylinder bores communicate via bores Ell, plunger bores and bore 48d with outlet bore 3 provided in shaft 2. When moved to the right the motor cylinder bores are in communication with bore l8 of tube 46. The fluid flow through pump cylinder block is similarly controlled. When plungers i9a move to the left, fluid flows from the working cylinders via bores 5%, the plunger bores and bores '43 to bore I8 and thus to the motor. When plungers l9a move to the right, fluid flows from bore 42a of shaft 42 through radial bores 48b, plunger bores, bores 50 to the pump cylinder bores.

Both the casings 9 and 45 are coupled to the respective motor cylinder block I4 and. pump cylinder block 44 by an Oldham type coupling ring 49. This ring has diametrically opposed grooves on opposite sides respectively receiving a key 5| on the cylinder blocks and further keys on the inner end walls of casings'9 and 45.

The casing '45 rotates with equal eccentricity about the main axes while casing 9 has an adjustable eccentricity.

'An output gear 16 is embodied with the shaft 2 and the input gear 13 with shaft 40. The hollow shaft 40 is driven by gear 13 as stated from an engine or motor not shown, and imparts rotat-ion to frame 32 and eccentrics 3| and 3B and cam 28. These eccentrics 3| and 38 cause an oscillating movement of casing 45 whereby the pump istons are actuated with wobble plate 20a actuating valve plungers I911. The pressure reaction of the pump pistons on casing 45 tends to rotate the same. This torque is transmitted to pump cylinder block 44 by coupling 49 and thereby to driven shaft 2. Owing to the reaction, however, a part of the output will always be transmitted immediately to driven shaft 2. The fluid is conducted as indicated by arrow R' from a reservoir, not shown, through a flexible conduit 54 which connects with a pipe 55 supported by a bracket 56 mounted on fixed outer casing l. The pipe 55 in turn communicates with hollow shaft 42 with respect to which it is rotatable but in fluid tight relationship. The hollow shaft 42 is integral with pump cylinder block 44.

Asimilar arrangement is also provided at the motor unit where the hollow shaft 2 integral with motor cylinder blockis rotatable with respect to but in fluid tight relationship with a pipe 57. This ipe 51 is supported by a bracket 58 mounted on the fixed outer casingjl. The fluid flows from the motor back to the reservoir, not shown, through pipe 51.

What I claim is: v

1. A hydraulic transmission comprising a fixed outer casing, a rotatable frame journalled Within said fixed outer casing and having eccentrics thereon, means for imparting rotation to said rotatable frame, a cylindrical inner casing rotatably mounted on said eccentrics, a pump including a rotor body within said cylindrical inner casing and having valves and radially disposed pistons, said pistons being mounted in cylinder bores and at one end bearing on the inner wall of the cylindrical inner casing, means forconducting fluid to the pump rotor body and means for operating the valves of the pump rotor body, a second frame within said fixed outer casing, means adjustably securing the second frame against rotation with respect to the fixed outer casing, a second cylindrical inner casing within saidse'cond frame and having eccentrics thereon journalling the second casing for rotation with respect to the s econdfframe, a motor including a rotor body within said second cylindrical casing and havingvalves and radially disposed pistons, said pistons being mounted in cylinder bores and at one end bearing on the inner wall of the second cylindrical casing, 'means for conducting fluid from the motor rotor body and means for opera-ting the valves of the motor rotor body, means for receiving torque from the motor, and a hollow shait rigidly interconnecting the pump and motor rotor bodies for conjoint rotation and for conducting fluid under pressure from the pump to th motor.

)2, A hydraulic transmission comprising a fixe'd outer casing, a first and rotatable frame jour' nalled within said fixed outer casing and having an eccentric and a cam at one end and an eccentric at the other end, means for imparting rotation to said rotatable frame, a cylindrical inner casing rotatably mounted on the eccentrics, a pump including a rotor body having cylinder bores and valve bores therein, said rotor body being within said cylindrical inner casing, valves and radially disposed pistons in the valve and cylinder bores respectively and the pistons bearing on the inner wall of the cylindrical inner casing, means for conducting fluid to said pump, a Wobble plate mounted on the cam for operating the valves of the pump, a second frame within said fixed outer casing, means adjustably securing the second frame against rotation with respect to the fixed outer casing, a second cylindrical inner casing within said second frame and having eccentrics thereon journalling the second casing for rotation with respect to the second frame, a motor including rotor body having cylinder bores and valve bores therein, said body being within said second cylindrical casing and having valves and radially disposed pistons in the valve and cylinder bores respectively and the pistons bearing on the inner Wall of the second cylindrical casing, means for conducting fluid from the motor, a flanged tube supported on the fixed outer casing and a wobble plate mounted thereon for operating the valves of the motor, means for receiving torque from the motor, and a hollow shaft rigidly interconnecting the pump and motor rotor bodies for conjoint rotation and for conducting fluid under pressure from the pump to the motor.

3. A hydraulic transmission comprising a fixed outer casing, a rotatable frame journalled within said fixed outer casing and having eccentrics thereon, means for imparting rotation to said rotatable frame, a cylindrical inner casing rotatably mounted on said eccentrics and having parallel guide flanges on its inner Wall, a pump including a rotor body within said cylindrical inner casing, said pump rotor body having radial cylinder bores and valve bores therein, valves and. radially disposed pistons in the valve and cylinder bores respectively, said pistons being constrained between said parallel guide flanges and bearing on the inner wall of the cylindrical inner casing, means for conducting fluid to the pump and means for operating the valves of the latter, a second frame within said fixed outer casing, means adjustably securing the second frame against rotation with respect to the fixed outer casing, a second cylindrical inner casing within said second frame and having eccentrics thereon journalling the second casing for rotation with respect to the second frame, said second casing having parallel guide flanges on its inner periphery, a motor including a rotor body within said second cylindrical casing, said motor rotor body having radial cylinder bores and valve bores therein, valves and radially disposed pistons within the valve and cylinder bores respectively and said pistons being constrained between said parallel guide flanges and bearing on the inner wall of the second cylindrical inner casing, means for conducting fluid from the motor and means for operating the valves of the latter, means for receiving torque from the motor, and a hollow shaft rigidly interconnecting the pump and motor rotor bodies for conjoint rotation and for conducting fluid under pressure from the pump to the motor.

4. A hydraulic transmission including a fixed outer casing, a rotatable frame journalled within said fixed outer casing and having eccentrics thereon, means including a first hollow shaft for imparting rotation to said rotatable frame, a cylindrical inner casing rotatably mounted on said eccentrics, a pump including a rotor body within said cylindrical inner casing, said pump rotor body having radial cylinder bores and valve bores therein, valves and radially disposed pistons in the valve and cylinder bores respectively, said pistons bearing on the inner wall of the cylindrical inner casing, means including a second hollow shaft concentrically positioned within the first hollow shaft and secured to the pump rotor body for journalling the pump within the cylindrical inner casing and for conducting fluid to the pump, means for operating the valves of the pump, a second frame within said fixed outer casing, means adjustably securing the second frame against rotation with respect to the fixed outer casing, a second cylindrical inner casing within said second frame and having eccentrics thereon journalling the second casing for rotation with respect to the second frame, a motor including a rotor body within said second cylindrical casing, said motor rotor body having radial cylinder bores and valve bores therein, valves and radially disposed pistons in the valve and cylinder bores respectively, said pistons bearing on the inner wall of the second cylindrical casing, means including a hollow shaft secured to the motor rotor body for journalling the motor within the fixed outer casing, taking off torque from the latter, and conducting fluid under pressure from the motor, means for operating the valves of the motor, and a hollow shaft rigidly interconnecting the pump and motor rotor bodies for conjoint rotation and for conducting fluid under pressure from the pump to the motor.

EDUARD WILLIAM WOYDT.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,173,432 Benedek Sept. 19, 1939 2,220,636 Bischof Nov. 5, 1940 2,458,985 Ferris et a1. Jan. 11, 1949 

